Per- and polyfluoroalkyl substances (PFAS) are prevalent chemicals of concern in groundwater. These compounds were contained in aqueous film-forming foam (AFFF), which was used to suppress fires at hundreds of sites and poses a serious human health risk. PFAS removal from groundwater is complicated by low volatility, general lack of reactivity to biodegradation and traditional oxidative treatment processes, and poor desorption kinetics from granular activated carbon (GAC) and other sorbents. Therefore, novel and effective remediation technologies are needed to remediate PFAS present in groundwater and aqueous concentrates.
The overall objective of this work is to develop efficient electrocatalysts for the reductive defluorination of PFAS that are present in groundwater and aqueous concentrates. Electrocatalysts will be deposited on a reactive electrochemical membrane (REM) support to take advantage of the high specific surface area and the efficient mass transfer that is achieved in the REM reactor during flow through operation. Specific objectives of this research include the following:
- Synthesis of electrocatalysts for PFAS reduction;
- Determination of the effects of natural water constituents on PFAS removal;
- Minimization of halogenated byproduct formation;
- Determination of the stability of electrocatalysts using longevity studies; and
- Calculation of costs for ex situ remediation of PFAS-impacted groundwater and PFAS concentrates using the electrocatalytic REM system.
In order to address the project objectives, the project team will innovate on its past work related to Ni-based reductive catalysis and REM synthesis and develop an electrocatalytic REM system that is capable of complete reductive defluorination of various PFAS, without the formation of short-chain PFAS or halogenated byproducts. The transformative nature of the research is the selective destruction of PFAS in a highly efficient REM flow-through reactor.
The work plan for this research consists of a series of bench-scale experimental studies that will determine optimal operating conditions for PFAS reduction in groundwater and aqueous concentrate samples. The main tasks of this research include the following:
- Electrocatalyst synthesis and characterization;
- Bench-scale catalyst screening studies;
- Study of the effects of non-target water constituents;
- Longevity studies; and
- Cost analyses.
The work is projected to end with proof-of-concept data that indicates the system is ready for scale-up to pilot testing at a groundwater site and/or for PFAS concentrate management.
The successful completion of this project will have numerous benefits to DoD and the scientific community. These include 1) a better understanding of the use of electrochemical technologies for groundwater remediation; 2) the development of a bench-scale electrocatalytic REM system that can reduce PFAS in impacted groundwater and aqueous concentrates to below the 70 ng L-1 treatment goal; and 3) cost assessments for using the REM technology for electrocatalytic PFAS destruction, which can be used by practitioners to assess the REM technology as a viable remediation option.